Method of digesting wood pulp



(No Model.)

M. L. GRIFFIN & P. 0. LARSEIL.

METHOD OF DIGESTING WOOD PULP.

No. 551,890. Patented Dec. 24, 1895.

r UNITED STATES PATENT OFFICE.

MARTIN L. GRIFFIN AND PETTER o'r'ro LARSEN, F LIEQIIANICSVILLE,

' NEW YoRK.

MET-HO D OF DIGESTING wooo PULP.

SPECIFICATION forming part of Letters Patent No. 551,890, dated December24, 1895. Application filed N v m er 30, 1894. Serial No. 530,423. (In;specimens.)

steady and continuous increase in energy during the operation ofcooking, insuring a continuous and steady rise in temperature of thewhole mass, and utilizing the excess of gas and liquor during the firstpart of the operation before the cooking commences, and also utilizingthe excess of gas, liquor, and steam during the'cooking operation bydischarging the same into a succeeding charge of liquor in a tankcontaining partially-prepared liquor and thereafter supplying thedigester with this prepared cooking liquor.

In carrying out this invention it is preferably employedin connectionwith the wellknown process of digesting wood by the sulphite process.

In the accompanying drawing is shown an apparatus to illustrate themanner of working this process, consisting of a digester, a

tank for containing the partially-prepared cooking liquor,- a blow-0Epipe connecting the digester with said tank, and so much of thewell-known pipe connections as are necessary for setting forth thisinvention.

A is the digester constructed in the wellknown way for digesting woodpulp and provided with the opening B in its top through which the chargeof wood is passed into the digester, and having the cover 0 adapted tobe secured over the opening B.

In charging the digester it ,is preferably practically filledwith chipsof wood and supplied with cooking liquor through any suitable pipeconnection-'as, for example, the

pipe H shown as broken away and connected with a suitable supply-tank F.

I is a blow-01f valve for the discharge of the cooked mass. c

The cooking liquor is supplied so as to cover the chips of wood, leavingno appreciable space for condensation of steam.

The cooking liquor may, for example, be composed of about one and forty.one-hundredths to one and fifty one-hundredths per cent. of lime,magnesia or other, alkaline base; about one and seventy-fiveone-hundredths per cent. of combined sulphurous-acid gas, and about twoand fifty one-hundredths per cent. to two and seventy-fiveone-hundredths per cent. of free sulphurous-acid gas.

In the commencement of the operation, steam is admitted to the digesterthrough the pipe D from a suitable source. To facilitate the admissionof the steam and provide for condensation a pipe E is employed ofsuitable acid-resisting material, which is constorage reservoir or tankF, containing a charge of partially-prepared cooking liquor having aboutone and fifty one-hundredths per cent. of baseand one and seventyone-hundredths per cent.'of combined and the same amount of freesulphurons-acid gas. This partially-prepared liquor is in this waysupercharged with s'ulphurous-acid gas, which renders the liquor moreefficient in the cooking, .producing a whiter and more uniformlycookedmass. The pipe E is provided with a valve G by means of which the flowof liq uor, gas, and steam through pipe E from the digester A to thetank F is regulated.

. As heretofore stated, in the commencement of the operation steam froma battery of boi iers is admitted to the digester through pipes I), thevalve G is opened and a'continuous discharge of liquor andgas fromdigester A into tank F, containing the partly-prepared cooking liquor,takes place during the first part of the operation, until thetemperature of the mass in the digester reaches abput 212 Fahrenheit,and after said temperature is reached and the cooking commencesacontinuous discharge of liquor, gas and steam takes place from digesterA into the tank F, containing the partially-prepared cooking liquor. During this operation, properly conducted, we are able to raise andmaintain the proper pressure and degree of heat by so regulating thevalve G that it will discharge only a volume of liquid equivalent to theamount of steam entering the digester through the valve D. For instance,suppose we admit steam to digester at eighty pounds pressure through athree-inch pipe and valve D, the area of whose orifice is seven squareinches.- It would require an orifice at G whose area was foufandnine-tenths square inches to discharge the water of condensation underpractically no head, while at the same time the temperature of thecontents of the digester wouldbe continuously rising. ;As soon as atemperature of reached, when an orifice, as at G, whose area is;

only twenty-five one-thousandths of a square inch will be ample for thedischarge of the condensation of the current of steam entering at fullhead through the orifice at D, and pro- .vided the same would be allcondensed, which of course it would not.

Neither wouldit be necessary, but in fact undesirable, to admit acontinuous current of steam ,of a constantquantity during the wholeperiod of cooking.

The amount of liquor to be discharged will be equivalent to the amountof condensation of the steam, which will be about twenty per cent. ofthe quantity contained in the digester. It will be necessary to relievethe gas and liqnor in such quantities continuously. as to insure acontinuous rise in the temperature of the mass.

As the bulk of the condensation takes place in raising the mass to 212Fahrenheit before the liquor exerts any marked cooking action,

the liquor displaced by the con'densation'of steam is available for asubsequent cooking operation, and the excess of gas dischargedsimultaneously with the liquor into the tank D will increase thestrength of the liquor contained in it from about three and fortyonehundredths per cent. ofsulphurous-acid gas to about four andfiftyone-hundredths per cent., besides raising the temperature of thesame to a considerable degree.

It has been the practice when the pressure in the digester is equal, ornearly so, to the pressure of the steam entering, and the temperature ofthe contents of the digester does 1 not correspond to the pressure, torelieve an afresh and quickly raising the temperature through anindefinite numberof degrees,until as follows:

The advantages of our improved process are First; At the beginning ofthe cooking operation we set the steam-valve for the steam entering thedigester so as to insure a cont-1nuous and steady flow of live steaminto the I mass to becooked.

Second. At the same time we open the valve G in the dischargepipe justenough to discharge a volume of liquor equal to that resulting from thecondensation of the entering steam,.and thereby insure a continuous andsteady rise in temperature of the entire mass.

Third. By our process we carry forward the entire operation of cookingthe wood by a steady and continuous increment of energy, including thepreparation of and adaptation of the liquor best suited for themechanical part of the process set forth, thereby eliminating thecontingencies and uncertainties attendant upon the present mode ofreducing wood to fiber.

Fourth. We are also able'to reduce the labor properly adjusted nofurther labor or attention vbecomes necessary until near the close oftheoperation, whereas with the present mode of procedure the constantattention of skilled 7 cocks is required.

Having now described our invention, what we claim is Q 1. The hereindescribed method of digesting i wood by the sulphite process, whichconsists in admitting steam to the digester containing a charge of chipsand cooking liquor, maintaining a continuous discharge of liquor and gasfrom the digester into a tank containing partly prepared cooking liquor,until the cooking begins, and then maintaining a continuous admission ofsteam into the digester and a continuous discharge of liquor, gas andsteam wood, which consists in filling the. digester practically full ofchips and cooking liquor.

covering the chips, admitting steam to the digester, maintaining acontinuous discharge of liquor and gastrom the digester into atankcontainingpartlyprepared cookingliquor uno ls acid gas for thepreparation of a fresh til' the cooking begins, regulating the dischargeof cooking liquor. charge of steam entering the digester, and Inwitnesswhereof wehave hereuntosetour maintaining during the cooking acontinuous hands this 14th day of November, 1894.

,5 admission of steam into the digester and a 7 continuous discharge ofliquor, gas and steam MARTIN GRIFFIN into the tank of partly preparedcooking 1iq- PETTER. OTTO LARSEN' uor containing about one and one-halfper Vlitnesses: I cent; of lime orother alkaline base, and three NEWTONT. BRYAN,

1o andfortyone-hundredthspercent.of sulphur- FRANK A. CURLEY.

